608 CLASS X. 



the first pair of feet ; in the long-tailed it is a fissure that extends 

 along the entire thorax on each side. The water is expelled, on 

 the other hand, along a furrow which opens forwards by the side of 

 the mouth. In this canal an oval lamina is situated, which is the 

 outermost lobe of the second pair of maxilla3, and produces by its 

 motion a current forwards to force the water out 1 . 



In nearly all crustaceans the two sexes are distinct. In the 

 Cirripedia, indeed, formerly counted amongst the Molluscs, the 

 male and female sexual organs are united in the same individual 2 : 

 [except in certain genera of the Lepadicea, as Ibla and Scalpellum 

 LEACH, where there are not only, according to DARWIN, males and 

 females distinct, but also the surprising fact of 'hermaphrodites 

 whose masculine efficiency is aided by one or more complemental 

 males 3 ,' often exceedingly minute, and rudimentary in structure, 

 which are permanently attached to different parts of the female.] 

 The ovary lies as an apparently granular mass in the pedicle of Ana- 

 tifa, and under the microscope is seen to be composed of rounded 

 lobes ; a tube which traverses the pedicle and opens into the mantle 

 above by a fine aperture on the dorsal surface is the oviduct. In 

 Balanus the ovary lies in the walls of the mantle. [According to 

 DARWIN the female organs consist of true ovaria (salivary glands 

 Guv.) seated on each side near the base of the labrum, of unbranched 

 ovarian ducts and of ovarian branching tubes and coeca. In the 

 Lepadicea the ovarian tubes branch out in all directions within the 

 peduncle, and ova are developed in the footstalks of their branches 

 as well as at their ends. Two unbranched tubes enter the body of 

 the Cirripede from the peduncle and run into the two true ovaria 

 situated at the base of the labrum and resting on the upper edge of 



1 See MILNE EDWARDS Reckerches sur le mecanisme de la respiration chez les Crus- 

 taces. Ann. des Sc. not. 2e SeVie, Tom. xi. Zoolorjie, pp. 129 142. 



2 A few years ago GOODSIB described small crustaceans, with five pairs of feet, as 

 the males of Balanus, Edirib. new Philos. Journ. xxv. 1843, p. 88, Ann. des. Sc. not. 

 3ieme SeV. I. 1844, pp. 107 117. These supposed male individuals present however 

 little or no resemblance to the juvenile form of Cirripedes, as we have been taught to 

 know them by BDRMEISTEB. 



3 DARWIN Lepadidce, 1851, p. 182. DARWIN found the animals described by 

 GOODSIR not to be males but females distended with ova. He considers them to be the 

 females of the unnamed genus belonging to the family of loniens, described by GoOD- 

 SIR, which live parasitically within the sac of the Balani. See DARWIN Monogr. of 

 the Cirripedia, Balani da>. London, 1853, p. 271. 



